Abstract
Abstract The changes that occur in the microstructure of crystalline and amorphous Cu-P-Sn-Ni filler metals during the heating process were studied by high-temperature microscopy, and the composition of solders at certain temperatures were analyzed by scanning electron microscopy and X-ray diffraction. The amorphous solder was observed to transform from amorphic to crystalline during the process of heating and distinct surface morphology changes were apparent, while the internal structure of the crystalline brazing filler metal was found to be relatively stable. During the heating process, the amorphous brazing filler metal formed a ϒ-Cu solid solution with a small amount of Cu3P compounds, Cu88Sn22 and (Cu, Ni)3P phase compounds, ultimately forming the Cu88Sn22 + Ni12P5 + (Cu, Ni)3P3 three-element eutectic structure.
Highlights
The changes that occur in the microstructure of crystalline and amorphous Cu-P-Sn-Ni filler metals during the heating process were studied by high-temperature microscopy, and the composition of solders at certain temperatures were analyzed by scanning electron microscopy and X-ray diffraction
The amorphous Cu-P-based filler metal is an amorphous material obtained by rapid cooling when the filler metal is in a liquid state
During the crystallization process of the amorphous filler metal as it nucleates and grows in the solid phase, the grain growth of the amorphous filler metal is mainly composed of equiaxed grains while that of the crystalline filler is mainly dendrites; and these dissimilar grain growth processes would affect the properties of the brazed joints [11,12,13,14]
Summary
The amorphous Cu-P-based filler metal is an amorphous material obtained by rapid cooling when the filler metal is in a liquid state. In the process of rapid cooling, crystallization of the filler metal can be induced when the material deviates from an equilibrium state. The amorphous Cu-P-based filler metal will preserve its atomic structure exhibited while in the liquid state, and these properties will imbue the amorphous filler metal with high toughness,. When a crystalline solder reaches its melting point, it wets and spreads on the base metal material until it cools and solidifies to complete the brazing process [8,9,10]. Decristofaro et al have reported early studies of amorphous Ni-based solders indicating that joints brazed with amorphous brazing materials have superior properties. 76.82 7.57 8.99 6.63 ing process, and the differences and relations between the amorphous and crystalline filler metals are discussed
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